Earth’s magnetic field is partly responsible for a couple of things that all humans enjoy. Firstly, it conspires with the solar wind to create those beautiful, ephemeral aurorae. Secondly, by preventing so much damaging radiation making it to the surface, it stops us all dying – that, inarguably, is rather wonderful.
As a new study in Physical Review Letters has revealed, though, there was recently a “crack” in it.
Back in June 2015, the GRAPES-3 muon telescope based in India – one which is designed to pick up on highly energetic interactions – spotted an increase in the flow of galactic cosmic rays (GCRs) permeating through our atmosphere. This type of radiation originates from outside our Solar System, although in this case, its source appeared to be relatively close by in our stellar neighborhood.
A detailed analysis led by researchers at the Tata Institute of Fundamental Research (TIFR) found that the plasma cloud got through an unusual, temporary gap in Earth’s magnetic field.
This GCR invasion coincided with a coronal mass ejection moving at 2.5 million kilometers per hour (1.6 million miles per hour), one that was so energetic that it caused the entire planet’s magnetic field to shrink from being 11 times the radius of Earth to just four times that. As reported by Wired, this triggered a geomagnetic storm that both boosted the dramatic iridescence of the Northern Lights, but also brought down radio networks for some time.
This storm was ranked as a G4 on the National Oceanic and Atmospheric Administration (NOAA) scale, which means it was rated as “severe”. It is highly likely that this powerful storm caused the crack to appear.
A powerful coronal mass ejection seen emerging from the Sun on August 31, 2012. NASA
These storms have the potential to cause trillions of dollars of damage to communications networks and electrical grids, and even endanger the lives of astronauts onboard the International Space Station. In fact, the team note in their study that “depending on the orbital variation of the cutoff rigidities, the astronauts on the International Space Station would have received a high, and variable radiation dose during the burst.” This would have included NASA astronaut Scott Kelly, who spent 340 days in low-Earth orbit.
Fortunately, the crack lasted for just a few hours, and the magnetic field returned to its original size and strength shortly afterwards. There’s a good chance that this astrophysical injury would have occurred in Earth’s past, but this particular phenomenon just hasn’t been detected until now. Of course, it’s almost certain that it will happen again.
If anything, this study is a powerful reminder of how frighteningly energetic our local star actually is. There’s pretty much nothing we can do about its violent outbursts, but a better understanding of their behavior can allow us to prepare for future geomagnetic storms.